Disk brakes system for rail and commercial vehicles that can be actuated by pressure medium exhibit in their design as caliper constructions a piston that is guided pressure-tight in a housing or in the caliper construction and can be actuated by hydraulic or pneumatic pressure medium and that acts relative to a brake shoe when actuated, in order to force said brake shoe with its brake lining against a brake disk to be braked. Linings that make contact by such working pistons in calipers make small transverse movements due to their bearing play; thus, a transverse force, which corresponds to the product of the piston force and the coefficient of friction (back of lining/piston), is impressed on the piston.
Laterally movable pressure plates, which are integrated into the piston face, reduce these transverse forces in proportion to the coefficients of friction; the pressure plates can be positioned with little friction and carry out lateral movements within predetermined limits against the resistance of the lateral spring elements, when the brake disk is engaged. When the brake is released, the elastic return elements return the pressure plate with a force that is proportional to their deflection. The drawback of such arrangements is that the friction, caused, among other things, by seals, prevents a return of the pressure plate to the zero value. The residual deflection of the pressure plate prevents the displaceability upon subsequent braking and leads, furthermore, to a disproportionately high lateral migration, when braking is in the opposite direction of rotation.